(a) Field of the Invention
The present invention relates to a hydraulic control system of an eight-speed automatic transmission for vehicles. More particularly, the present invention relates to a hydraulic control system of an eight-speed automatic transmission for vehicles that minimizes shift shock and improves shift performance and fuel consumption by realizing precise control.
(b) Description of the Related Art
Typical automatic transmissions include a torque converter and a power train of a multiple speed gear mechanism connected to the torque converter. In addition, a hydraulic control system is provided at an automatic transmission for selectively operating at least one operational element included in the power train according to a running state of a vehicle.
Such an automatic transmission includes a power train and a hydraulic control system. The power train includes a compound planetary gear set, formed by combining at least two simple planetary gear sets to achieve the required multiple speeds, and a plurality of friction members. The hydraulic control system selectively operates the friction members of the power train according to driving conditions.
A variety of such power trains and hydraulic control systems have been developed by vehicle manufacturers according to their own schemes. Currently, four-speed automatic transmissions are most often found on the market. However, six-speed and seven-speed automatic transmissions have also been realized for enhancement of performance of power transmission and for enhanced fuel mileage of a vehicle.
Recently, developing further from such seven-speed automatic transmissions, eight-speed automatic transmissions are under investigation such that performance of power transmission of an automatic transmission, and thereby fuel mileage of a vehicle, are being further enhanced.
The above information disclosed in this Background section is only for enhancement of understanding of the Background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.